Regulator applicable for helicopter rotors



REGULATOR APPLICABLE FOR HELICOPTER ROTORS Filed Oct. 5, 1949 3 Sheets-Sheet l y 25, 1954 P. MORAIN 2,679,296

REGULATOR APPLICABLE FOR HELICOPTER ROTORS Filed Oct. 5, 1949 s Sheets-Sheet 2 P. MORAIN REGULATOR APPLICABLE FOR HELICOPTER ROTORS Filed Oct. 5, 1949 May 25, 1954 3 Sheets-Sheet 3 lmmnuml Patented May 25, 1954 REGULATOR APPLICABLE FOR HELICOPTER ROTORS Paul Morain, Paris, France, assignor to Societe Nationale de Constructions Aeronautiques du Sud-Ouest (Societe Anonyme), Paris, France,

a company of France Application October 5, 1949, Serial No. 119,631

Claims priority, application France October 14, 1948 Claims.

Speed governors are already known which comprise a differential gear train whos sun gears are driven respectively by a shaft rotatively connected to a device the speed of which is to be adjusted, and by a reference speed source, and whose toothed case containing the planet gears is connected to a member controlling the speed of the engin driving said device. Such a governor is described in U. S. Patent No. 2,269,332.

Any difference between the reference speed and the speed to be adjusted causes the differ ential case to rotate and hence causes an appropriate corrective action on the driving engine.

Although satisfactory in principle, these governors entail however serious drawbacks.

First, such a governor does not by itself provide for any damping and, in the absence of any physical factor causing this damping, it gives rise, after a disturbance, to successive alternating corrections which cause the speed to be adjusted to oscillate indefinitely about its initial value.

Further, th power required for effecting the correction being supplied partly by the above device, and partly by the reference speed source, the load assigned to that source may alter its speed and disturb the action of the governor.

Moreover the use of a reference speed source other than the device to be adjusted, constitutes a drawback.

According to the invention, the speed governor device for a rotary system comprises a differential gear train associated on the one hand with said rotary system and on the other hand with a reference source of constant-velocity rotation, said differential gear train being further associated with a member adapted to move at a velocity corresponding to the differential velocity of said rotary system with respect to said reference source, characterized in that said member is connected to the control means of the rotary system through two mechanical transmissions of different gear ratios each of which is provided with coupling means adapted to be selectively controlled by means responsive to the direction of the acceleration of said member and means responsive to the direction of the velocity thereof, associated with one another, the arrangement being such that the lower gear ratio transmission is coupled when the acceleration and the velocity of said member are of the same sign, and

the higher gear ratio transmission is coupled when the acceleration and the velocity of said member are of opposite signs.

This arrangement causes the governor to have a damped period, even when the opposing torque of the device to be adjusted is independent of the speed.

According to a further improvement, the reference source is constituted by a shaft driven by the engine of the device to be adjusted through a friction clutch subjected to the opposed efforts of centrifugal force and of a return spring. This kind of constant speed drive is known. It is often used, for instance, in gramophones for insuring constant-velocity rotation of the record. However, as far as I am aware it has not been proposed up to now to use it as a constant speed source for governors such as those to which the invention refers. However, the constant speed thus achieved is strongly influenced, at any rate temporarily, by the variations of the opposing torque of the shaft the speed of which is kept constant. In order to prevent the regulation energy supplied by this shaft from altering its speed, the driving friction is further subjected to a torque adjusting device, so that this friction becomes more active as the power supplied by the shaft increases and vice versa.

Besides, the action of the friction clutch return spring is made to be automatically adjustable in operation in such a way that, when the speed of the driven device is willingly altered, the speed of the friction driven shaft gets adjusted to that of the device, so that this new adjusted speed may be automatically maintained by the governor.

The invention further includes the application of such improved governors to helicopter rotors, as well as transmission members for this application.

Qther features and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing forming a part of this application and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a diagram of a known governor.

Fig. 2 is a diagram of the mechanisms and electric circuits which ensure automatically a varying efficiency to the corrector when the acceleration or the speed of the planet gear case changes sign,

Fig. 3 shows a friction mechanism according to the invention in which the centrifugal force is balanced by a return spring,

Fig. 4 is a general diagram of the governor according to the invention,

Figs. 5 and 6 are diagrams relating to the application of the governor to the regulation of a plurality number of engines,

Fig. 7 is a perspective general diagram illustrating a rotor-engine control as applied to a helicopter,

Fig. 8 is a large scale section of the upper end of the hand control,

Fig. 9 is a cross-section taken along line IX-IX of Fig. 8,

Fig. 10 is an electric diagram of the network and members connected to the hand control illustrated in Figs. 7 to 9.

Referring to Fig. 1, I20 denotes a shaft which is driven by any suitable source of power diagrammatically shown at A, at a constant angular speed I2I denotes another shaft which is driven by any suitable source of power diagrammatically shown at B at an angular speed w which it is intended to maintain at the same absolute value as the reference or standard angular speed w Operatively interposed between shafts I20, I2I is a control differential system, for example one having bevel gear wheels, which comprises a sun gear I fast with shaft I2I, another sun gear 2 fast with shaft I20, planet gears 3, 3 meshing with sun gears I, 2, and a toothed case 4 which pivotally supports said planet gears. Meshing with case 4 is a gear illustrated as a toothed wheel 5, for displacing a lever 6 which acts on a memher (not shown) controlling the driving torque of the driven device and adjusting the speed of shaft I2 I.

It will be seen that if w=w in absolute value, planet wheels 3 and 3 rotate about their axes without driving case 4; but if, for example, no is greater than w case 4 is at once driven in the direction of the arrow at an angular speed ww and acts in the proper direction through lever B on the torque control member (not shown) at a speed proportional to ww,,, thereby providing a very sensitive and powerful governor. The lever B may act on the control member either directly or through an auxiliary motor of any known type. It appears at once that it is a delicate problem to secure for sun gear 2 a sufficiently constant angular speed w for achieving the sensitiveness required from the governor, by means of a torque capable of moving the adjusting members without affecting the constancy of said speed.

In addition to the above diificulty which is readily apparent, a governor of the type described with reference to Fig. 1 has a serious drawback The correction which is effected through the action of lever B on the speed of th shaft I2I exceeds that which would be sufficient for ensuring rotation at the speed of shaft I20. In other words, when w decreases, the lever B will move so as to cause an acceleration of shaft I2I; but the resulting increase in speed will not be stopped when this shaft reaches the speed w since, up to that moment, the lever 6 has continued moving in the sam direction. Therefore the speed of I2I starts exceeding w and the lever B is then driven in the opposite direction with the result that shaft I2I slows down. But again, its speed will decrease beyond w, and the lever B will move again in the initial direction, and so on. Thus the governor hunts indefinitely with a certain period and amplitude.

Th present invention has for its object to insert on shaft '5, between the differential gearing I2 -3-- l and the controlling member 6, a transmission gearing so designed that it will cause a damping action, thus avoiding the hunting phenomenon.

This transmission gearing includes two branches or paths which are alternately operated, these branches having different gear ratios and being controlled by a device which throws into gear one of them while it throws the other out of gear.

Fig. 2.

Fig. 2 diagrammatically shows an acceleration 'detector and a rotation direction detector developed' side by side. Actually both these detectors are arranged on a same shaft 1, the movement of which depends on that of the planet gear case 4, preferably with a gear step-up to provide for a more sensitive detection.

The acceleration detector comprises a disk 8 very freely mounted on shaft I (for example through a ball bearing i22), having a relatively high mass inertia and provided with a pair of resilient contact strips I2, I2 adapted to cooperate with either of two non-resilient contact studs I2a, I2a angularly spaced-apart on disk 8, when pushed by a finger IO fast with shaft I; as contact studs I2a, I2a are not resilient, they further provide abutments which, together with finger If cause disk 8 to be driven round by shaft I.

Brushes 9|, 9| in contact with ring conductors 92, 92 respectively are connected to a source of electric current through wires I23, I24 and I23, I24 respectively, while resilient contact strips I2, I2 are connected to a ring conductor 93 with which a brush 94 is arranged to 00- operate.

The rotation direction detector comprises a disk 9 having a relatively slight inertia, also very freely mounted on shaft I (for example through a ball bearing I25) and subjected to friction due to a brake-shoe 20 urged by a spring I29 fixed on a stationary part, for example the detector casing. Disk 9 carries a pair of resilient contact strips I3, I3 adapted to cooperate respectively with non-resilient contact studs I3a, I3'a when pushed by a finger II fast with shaft 1; being non-resilient, studs I3a, I3a provide abutments which together with finger II, cause disk 9 to be driven round by shaft I.

Brushes 96, 98 connected to source 90 through wires I26, I26 are in contact with ring conductors 95, 95' respectively energizing studs I3a, iSa, while resilient contact strips I3, I3 are connected to a ring conductor Bl with which a brush 93 is arranged to cooperate.

The switches formed by contacts I2, I2a and the like, are inserted in an electric circuit (diagrammatically shown on Fig. 2) comprising an electromagnetic relay I l; the armature I5 of this electro-magnet is urged away therefrom by a spring !6 and operates a two-way switch I! to energize either an electro-magnetic clutch I8 mounted on one of the branches of the transmission gearing (small gear-ratio between the planet gear case and the driving torque control) or an electro-magnetic clutch i9 mounted on the other branch of the transmission gearing (large gear ratio between the planet gear case and the driving torque control).

Let us assume that a disturbance in the opposing torque causes angular speed w to decrease;

the planet gear case starts to rotate with a speed w w, driving shaft 7 in a direction supposed to be that shown by the arrow F on Fig. 2. Owing to inertia, disk 8 has a tendency to remain stationary but finger it pushes strip I 2 to contact with stud life. Likewise disk 9 subjected to the friction of shoe tends to remain stationary, but finger ll pushes strip 3 to contact with stud lt'a, thus closing the circuit as switches I2-l2a and l3l3a are in series with 90. Hence electro-magnet i l is energized and switch If closes the energizing circuit of electro-magnctic clutchit which corresponds to the greater power of the governor. This action lasts as long as shaft I is accelerated, i. e., as long as its velocity (m -w) increases.

As soon as the acceleration is reversed, i. e., it starts acting in the opposite direction, the velocity of shaft stops increasing and starts decreasing, the direction of rotation'remaining still unchanged. But disk 3, by reason of inertia, tends to keep the same speed and 'finger l0 moves apart from strip l 2 thus breaking the circuit. It then pushes strip ii! to contact stud l2a. On the contrary, as the rotation direction has not changed, finger l 5 remains in contact with strip IS on disk The electro-magnet i l is not energized any longer, and switch ll opens the energizing circuit of clutch it while closing the energkzing cir lit of clutch [3, corresponding to the smaller so er of the governor.

the governor is used while this lag decreases. That is to say, the regulator reacts vigorously in the former case, but mildly in the latter one.

The clearance between fingers I0, I! and the corresponding strips l2, l2, I3, I 3 may be very small, so as to cause but a negligible lag in the control. The brushes associated to the rings of disk 9 may conveniently be employed as braking members instead of a separate brake-shoe 20. As a matter of fact, all brushes and ring conductors may be grouped in association with disk 9, and flexible conductors may be provided to connect disk 9 to contact members on disk 8 because the maximum angular shift between disks When the velocity (w w) of shaft 1, after reaching zero, starts increasing again (but in the opposite direction which now coincides with that of the acceleration), the high-inertia disk 8 causes finger it to remain in contact with strip l2, but finger ll pushes strip is to contact stud lea; hence magnet is is again energized since switches l2'! 2'11 and l3-i3a are in series with 90. Therefore clutch is is no longer energized and clutch is is energized again.

Lastly, as soon as the acceleration is again reversed, i. e., it starts acting in the initial direction, the velocity of shaft '1 after reaching a new maximum value, starts decreasing whil it direction of rotation is unchanged (now opposite to that of the acceleration). This causes finger it to slow down relatively to the high-inertia disk 8; contact |2-l2'a is broken and contact l2--l 2a is closed (contact lS-l to remaining unaffected since the direction of rotation is the same). Thus clutch i8 is deenergized while clutch i9 is energized.

To summarize, clutch l 8 will be energized every tim switches l2i2a and l3'l3'a or switches IZ'--l2'a and iii-Itaare simultaneously closed, i. e., every time the velocity of shaft 1 tends to increase whether it rotates in one direction or the other, or in other words the acceleration acts in the same direction as that of rotation. On the other hand, clutch is will be energized every time the velocity of shaft 1 tends to decrease whatever its direction, or in other words every time the acceleration acts in the direction opposite to that of rotation.

It will readily be understood that the speed and acceleration detecting device just described operates correctly whatever the direction of initial difference (L -c In other words, it is always the greater power of the governor which is first operated.

It is to be noted, as a result, that the greater power of the governor is used while th lag between the controlled member and the reference member increases, Whereas the smaller power of 8 and 9 is not greater than the maximum angu lar clearance between contact elements I2, l2 and l3, [3.

With a view to obtaining a constant reference speed from the device running at a variable speed w to be adjusted, a construction as shown on Fig. 3 may be employed. It is known that in a friction clutch, the centrifugal force is balanced by the action of a spring. Such a clutch is satisfactory as long as the opposing torque from the frictionally driven shaft is constant or varies but slowly. When the opposing torque varies suddenly, as in the case with the present governor Where, through the differential, a part of the torque required for operating the power control is supplied by the constant speed shaft, the driven shaft must be subjected to a considerable speed change in order that a substantial variation of centrifugal force alters the friction force in the clutch in the proper direction.

Shaft 34 whose angular speed is to be maintained constant by means to be described subsequently is connected to sun gear 2. A clutch drum 22 is integral with a toothed wheel 2| driven by the shaft whose speed is to be controlled, through a step-up gearin having a ratio such that the minimum velocity of the toothed wheel 2| is always greater than the constant reference Clutch shoes 23 are pivotally supported on,

levers 24, the pivot pins 25 of which are carried by arms 21 fast with a tubular shaft or sleeve 30 coaxial with shaft 34. A spring 28 backed by a nut 29 screwed on shaft 30 acts through a ring 3! and pins 32 on the arms of levers 24 remote from those which carry shoes 23. The ends of levers 24 proximate to pins 32 engage axial grooves 26a in one of the races of a helical thrust ball bearing 33. Accordingly, neglecting any angular shift imposed by thrust bearing 33, shafts 30 and 34 revolve at the same angular speed.

Let us first assume that the opposing torque on shaft 34 is small or nil. The centrifugal force developed by the combination of levers 24 and shoes 23 is balanced by spring 28 and the pressure of said shoes on drum 22. The friction in the clutch is just great enough to drive the combination of levers and shafts 30, 3d at the speed w, for which balance takes place. Let us now suppose that a considerable opposing torque occurs on shaft 34. The helical thrust bearing 33 (whose pitch is suitably selected with respect to the direction of rotation of shaft 36) will develop a thrust on the end 26 of levers 2 resulting in an additional pressure of shoes 23 on drum 22. The product of the additional pressure by the friction coefficient sets up an additional torque which, with a suitable leverage,

7 34. The speed will thus remain undisturbed by any variation of opposing torque.

Furthermore nut 29 which adjusts the tension of spring 28 is fast with one of the elements of a clutch 35, the other one being fast with a toothed wheel 36. If clutch 35 is shifted to operating position, for example by axially shifting wheel 36 by means of lever E00, and the toothed wheel is rotated at a speed w,, it will be seen that, with a properly selected pitch for nut 29, the adjustment of spring 28 is altered until shaft 34 revolves at speed (0,. If w, is greater than ca the movement of nut 29 increases the tension of spring 28 and consequently the friction of shoes 23; on the contrary if m, is smaller than w the tension of spring 28 and the friction decrease. Consequently an easy adjustment of the speed is obtained. If, in particular, at the time when the governor is uncoupled, clutch is thrown into gear and the adjustment of the driven mechanism is manually altered, toothed wheel 35 revolving at the speed or, these operations will result in automatic alteration of the tension of spring 28 in order that, when the governor is coupled again, the speed maintained automatically by the governor will be the same as obtained by manual adjustment, when the latter is replaced by that of the governor.

The various above described members may be grouped, by way of example, as diagrammatically shown on Fig. 4.

Keyed on a shaft 3? rotating at the angular speed to be controlled, is the sun wheel i. Through a toothed wheel i2! thereon, an intermediate pinion 38, and a toothed wheel 226 keyed on a shaft 39, shaft 3'5 drives said shaft 39 which in turn drives toothed wheels 2! and 3'3 of the constant speed clutch device 46 shown in detail in Fig. 3 through pinion 2 la and 33a, respectively. The planet gear case comprises a toothed ring 4 driving (preferably through a step up gearing) shaft '1 of the device 4! (shown in detail on Figure 2) comprising acceleration and rotation direction detectors 8-4 Two pairs of gears 40, 5: with different gear ratios are provided to drive toothed wheel 42 through clutch it or clutch 69 at two different angular speeds with respect to the planet gear case. A clutch 43 '5 provided to cause the governor to act or not to act on lever S for adjusting the power of the i engine. Clutch G3 is operated by means of a lever 45 which is further connected through a lever Iilfi to toothed wheel 38 adapted to adjust the tension of spring '38 (Fig. 3).

When the governor is uncoupled, by the clutch 43, the gear 35 is connected to the constantspeed clutch adjustment and vice-versa. Furthermore, clutch is being out of gear, a lever 44 enables lever 6 to be adjusted manually in order to obtain the desir d speed. Eventually the tension of spring 28 is auomatically adjusted so that said speed is maintained by the action of the governor when the latter is coupled again.

A governor system arranged according to this invention, is particularly suited for synchronizing several motors or engines remote and separate from one another, by applying only weak torque transmission means for which non-mechanical means may in fact be substituted.

Referring to Fig. 5, a pilot engine or motor :28 which may merely be an adjustable speed motor, simply adapted to supply governors with the required power regulates motors 48a, 482), 4312 to be adjusted. Through transmission devices 49a, 4%, 4912, the constant speed sun gears of governors 52a, 50?), 5M instead of being driven by constant speed clutches (that are now omitted) are driven by the pilot engine 48. The other sun gears of each differential couple are driven by the engines or motors to be adjusted, and each governor acts through a gearing IDIa, HHb, min on the corresponding engine.

Motors 5la, 5H), 5m controlling the varying speed sun gears, have been added in Fig. 6. These motors are synchronized with generators 52a, 521), 5212 which are operated by the engines 48a, 48b to be adjusted and connected to them through a transmission which may be electrical. Similarly, the linkages starting at the governors operate servo-motors whose transmissions 53a, 53b, 53TL control, for instance electrically, receivers 54a, Mb, 5811. acting on gearings rem, Hill), iiiln of the engines. It may thus be seen that there remains no mechanical link with the engines to be adjusted.

A governor arranged according to the invention is particularly well adapted to the regulation of the speed of helicopter rotors. The thrust of the rotor which balances the weight of the aircraft is proportional, for a given pitch of the blades, to the square of the speed. The opposing torque balanced by the driving torque is also proportional to the square of the speed. In order to control vertical displacements, it is thus possible to act either on the pitch, the speed remaining constant, or on the speed, the pitch remaining constant. The first alternative preferable since by acting on the speed, the response is less immediate owing to the inertia of the rotor. Besides, the speed of the rotor can only vary within narrow limits owing to centrifugal force and to the mechanical strength of the rotor.

Control through pitch variations therefore requires simultaneously a very accurate adjustment of the driving torque in order to keep the speed constant. It is impossible to render this adjustment sufficiently accurate by a mere combination of controls. A very accurate governor must complete the action of this combination. Moreover, the governor must meet any disturbance in the driving torque and automatically decrease the pitch in order to ensure self rotation in case of failure.

As described hereafter, it will be seen how a governor according to the invention, completed by particular control devices, may perfectly solve the problem set.

Fig. '7 shows such a rotor-engine control as applied to a helicopter. In this case, the controls of clutch 4t and of clutch 35 (Fig. 3) associated with lever I89 and pinion 36, are not mechanically coupled through a linkage 45 as in Fig. l, but are independently actuated by electromagnetic devices as and 85, respectively. Electromagnetic device 84 is adapted, when energized, to throw clutch 43 into gear, whereas electromagnetic device 85 is adapted to move pinion 35 into clutching position when deenergized.

The pitch and torque control members include a lever 56 pivotally mounted about a transverse axis 55-55 which controls through fork E5, the pitch control transmission 82. The direction of the arrows is, for instance, that which decreases the pitch. A hollow shaft 5i may rotate coaxially around the longitudinal axis of the pitch control lever; this shaft 6| drives the driving torque control transmission I03, through bevel pinions 62 and (the axis of the latter lying along 55*55). The direction of the arrows is that which decreases the driving torque. It may be seen for instance, provided shaft 6| is secured against rotation relatively to lever 55, that to decrease the pitch causes the driving torque to decrease. Thus a mechanical combination of the pitch and driving torque control transmission, is effected.

The exit shaft I M of the governor (Figs. 4 and 7 ends with a pinion 54. whose axis lies also along 55-55. The direction of the arrow is that corresponding to a decrease in the driving torque. The shaft 31 associated with the governor is connected to the rotor of the helicopter. The movement of pinion 513 is transmit ed to the controls through epicycloidal gears 53 and 59 keyed to a shaft til. rotating inside lever parallel to axis 55--55, pinions d and "58 and the pinions 58 and 59 forming an epicycloidal gear train. It may be seen that, provided the pitch control lever secured against pivoting (by locking means to be described hereafter) and provided the pinion til is free to rotate, the pinion 54 (rotating in the direction of the arrow) will cause the driving torque control gearing I03 to be displaced in the direction of the arrow, i. e., in the direction corresponding to a decrease in the driving torque. If, on the contrary, the pinion to is prevented from rotating (owing to abutments 66 or B5 to be described hereafter) while the pitch control lever is allowed to pivot, the pinion 56 will cause the pitch control gearing I92 to be displaced in the direction opposite to that of the arrow, i. e., in the direction corresponding to an increase in pitch or, in other words, to an increase in the opposing torque. 7 Thus the governor may act either on the driving torque, or on the opposing torque, but it will be seen hereafter that the governor normally acts on the driving torque, and it is only when it can no longer increase the torque that it interferes for reducing the pitch so as to reduce the opposing torque.

The head G3 or" the pitch lever 56 is shown in detail in Fig. 3 which is an axial section along a plane perpendicular to the rotation axis Eli -55, and in Fig. 9 which is a cross-section of this head 53.

Around the torque control hollow shaft iii, a handle ii may rotate, its angular displacement relatively to this shaft is limited by finger til and abutments l9 and #9. Two springs arranged between abutments is and is and fingers 8i and iii urge handle it to a mean fixed position relatively to shaft iii. In this position, an electric contact is established between brush 83 secured to the handle and the terminal of a sector 82 integral with shaft 6!. Thus as soon as shaft is rotated in either direction by means of handle ll, the electric contact breaks and is reestablished when the handle is released.

The pitch lever comprises further a pitch control handle is pivotally mounted about an axle 72 parallel to axis 55- 55 and whose angular displacement is limited by the clearance between a finely toothed ring it secured to the lower part of handle it and another symmetrical ring iii secured to the upper part of hollow shaft 6!. Two springs l7 and il handle it in a mean fixed position relatively to lever 56 and to shaft 3!. In this position, an electric contact is established between brush it; secured to handle is and the terminal of a sector integral with an extension 56a of lever Time, when pivoting handle it in either direction for altering the pitch of the rotor, the toothed rings i l and 14' are thrown into gear, thus securing against rotation shaft 5! with respect to lever 5t, and the torque control transmission is driven by the pitch lever simultaneously with the pitch transmission, thus achieving the desired mechanical combination. At the same time, the electric contacts lfi58a is broken. When handle I3 is released, shaft 6| is free to rotate and the electric contact is reestablished.

Lastly, lever 56 may be secured by means of a dog 6Q cooperating with a toothed sector 58'; when electromagnet i0 is energized, this dog engages sector 68.

Fig. 10 is a diagram of the network connecting the previous device and electromagnets 84 and 85 controlling respectively the throwing into gear of the governor and of the device altering the tension of the constant speed clutch spring. The same reference numbers are used as in Figs. 7, 8 and 9. Mechanical forming electric contacts iii and 68 are arranged. on the driving torque control transmission Hi3, corresponding to the maximum and minimum torques which may be achieved. When transmission I 93 abuts, electric contacts fifia on the one hand, fifi'a and 66'!) on the other hand, are broken. Similar abutments 6? and 57 forming electric contacts 610. and li'la are arranged on the pitch control transmission HJZ. A source I95 feeds these circuits. Lastly, the pilot may operate a switch 8! controlling the circuit of electromagnet 84. The control circuit of this electromagnet comprises in series contacts 82, 83 of handle ll and contacts 75, 56a of handle 73. The circuit of electromagnet 85 is directly closed by contacts 82, 83.

If either the driving torque control handle H is operated, or the pitch control handle 73, the electromagnet 84 is deenergized and the governor which is controlled thereby is thrown out of gear so that it is possible to alter at will the speed of the rotor or the pitch of its blades.

If the torque control handle H is operated, the electromagnet 85 controlling the device altering the tension of the spring of the constant speed clutch is deenergized, and hence it alters the adjustment of the speed to the desired value.

As soon as the pitch control handle 13 is operated, besides mechanically securing shaft Bl against rotation, electromagnet '58 being no longer energized, spring m6 unlocks sector 68 by acting on dog 69 and the pitch control lever is unlocked.

As soon as the torque control gearing l 83 meets either of abutments 56 or G6, the pitch control lever is also unlocked. Furthermore, in the case abutment occurs at 68 (maximum torque), besides the contact ttb, a further contact 55a is opened.

Lastly as soon as the pitch control transmission m2 meets either of abutments 6'! or 67', the governor is thrown out of gear.

Let the helicopter be flying, the governor ensuring a convenient and constant rate to the rotor. As soon as the pilot acts on the pitch control handle 13 for a vertical motion, he automatically unlocks the pitch control and secures shaft 8! and pinion 62 to this lever. The variation of the pitch causes a mechanical balancing of the couple. of gear and leaves complete driving freedom. As soon as this action stops, the pitch control lever is locked, pinion 52 is loosened and the governor completes adjusting the torqueto the value required for ensuring the steadiness of the speed.

The governor is thrown out i If the pilot wishes to alter this speed, by acting on the torque control handle H, he throws the governor out of gear and engages the adjusting device of the constant speed clutch, while altering simultaneously by the desired amount the torque adjustment. When he releases the handle, the governor is, at the same time, engaged and adjusted for keeping constant the new speed existing at the moment of the last engaging.

If, during automatic adjustment, the torque control transmission acts on either of the abutmerits 6B or 65', this transmission becomes cured against motion, the pitch control lever is unlocked and the governor acts on this lever and the pitch control transmission for maintaining the speed constant. This action may be geared down in a convenient ratio relatively to the action on the torque, by the appropriate choice of the gear-ratio of epicycloidal train i l-ii 59-60. This possibility occurs in particular in case of engine failure. The pitch is then decreased until the adjusting rate is reached in selfrotation.

If, when the governor acts on abutments of the pitch control transmission are reached, the governor is thrown out of gear so as to avoid injury to the mechanism.

The operation just described is possible during a normal flight far from the ground since, in this case, switch 8': is closed by the pilot.

On the contrary, during a near ground level, switch 81 will remain open. If an engine failure then occurs, the torque control transmission !63 will abut (both owing to the reflex action of the pilot and to the effect of the governor) against the stop 86 in the position of maximum torque. This causes contacts Gta and G6'b to open, and thus, the pitch control is unlocked, but the governor is simultaneously thrown out of gear, so that this governor cannot, as in normal flight, impose a decrease in pitch down to self-rotation rate, thus avoiding a sudden decrease in the lift which is particularly dangerous when the aircraft is near the ground.

It may be noticed that any action of the pilot on the pitch or on the torque automatically throws out of gear the governor, and that any action on the torque control handle (even during self-rotation) enables the pilot to alter the value of the constant speed which the governor is to keep.

I claim:

1. A speed responsive device for adjusting control means of the speed of a rotary system, Col. 1

prising a reference source of constant-velocity rotation; a differential gear train associated on the one hand with said rotary system, and on the other hand with said reference source; a shaft cooperating with said differential gear train, adapted to rotate at a velocity corresponding to the differential velocity of said rotary system with respect to said reference source; two mechanical transmissions of different gear ratios between said shaft and said control means; an

electrically operated clutch in each of said transmissions; a source of electric current connected to said clutches; a two-way switch between said source of electric current and said clutches, for selectively engaging said clutches; an electromagnetic relay for controlling said switch, said relay being adapted, when energized, to switch on the clutch in the lower gear ratio transmission and, when deenergized, to switch on the clutch .in the higher gear ratio transmission; an

the pitch, the

energizing circuit associated with said relay; a disk of relatively high inertia and a disk of relatively low inertia, both mounted for free rotation relatively to said shaft; a first switch in said circuit, including a resilient strip cooperating with a stop, both carried by said high-inertia disk; a second switch in said circuit, including a resilient strip cooperating with a stop, both carried by said high-inertia disk, said resilient strips being spaced from and adjacent to one another; a member secured against rotation relatively to said shaft and extending between said resilient strips, said member being adapted to urge either of said strips into contact with the respective stop and to drive the high-inertia disk in the corresponding direction; a third switch in said circuit, in series with said first switch, including a resilient strip cooperating with a stop, both carried by said low-inertia disk, the sequence of said first and last-mentioned resilient strips and stops being the same in a same direction around the shaft; a fourth switch in said circuit, in series with said second switch, including a resilient strip cooperating with a stop, both carried by said low-inertia disk, said third and fourth-mentioned resilient strips being spaced from and adjacent to one another; and a member secured against rotation relatively to said shaft and extending between said third and fourth-mentioned resilient strips, said latter-mentioned member being adapted to urge either of said lattermentioned resilient strip into contact, with the respective stop and to drive the low-inertia disk in the corresponding direction.

2. A speed responsive device according to claim 1, further comprising braking means associated with the low-inertia disk for increasing responsiveness thereof to th velocity of the shaft.

3. A speed responsive device for adjusting control means of the speed of a rotary system, comprising a reference source of constant-velocity rotation; a differential gear train associated on the one hand with said rotary system, and on the other hand with said reference source; a member cooperating with said differential gear train, adapted to move at a velocity corresponding to the differential velocity of said rotary system with respect to said reference source; two mechanical transmissions of different gear ratios between said member and said control means; a clutch in each of said transmissions; and clutch control means responsive to the directional components of the acceleration and velocity of said member for coupling the lower gear ratio transmission when said directional components of the acceleration and velocity of said member are in the same direction, and for coupling the higher gear ratio transmission when said directional components of the acceleration and velocity of said member are in the opposite direction.

4. A speed responsive device for adjusting control means of the speed of a rotary system, comprising a reference source of constontvelccity rotation; a differential gear train associated on the one hand with said rotary system, and on the other hand with said reference source; a member cooperating with said differential gear train, adapted to move at a velocity corresponding to the differential velocity of said rotary system with respect to said reference source; two mechanical transmissions of different gear ratios between said member and said control means; an electrically operated clutch in each of said transmissions; individual energizing means for said clutches; switching means for selectively controlling said energizing means; and switch control means responsive to the directional components of the acceleration and velocity of said member for switching on the energizin means of the clutch in the lower gear ratio transmission when said directional components of the acceleration and velocity of said member are in the same direction, and for switching on the energizing means of the clutch in the higher gear ratio transmission when the said directional components of the acceleration and velocity of said member are in the opposite direction.

5. A device according to claim 4, wherein the member is a shaft adapted to rotate at a velocity corresponding to the said difierential velocity, wherein the switching means comprise two mechanically independent groups of switches adapted to selectively control the energizing means, and wherein the switch control means comprise a disk of relatively high inertia mounted for free rotation relatively to said shaft, and adapted to control one of said groups of switches; abutting means on said disk; a member secured against rotation relatively to said shaft, and adapted to cooperate with said abutting means for driving said disk; a disk of relatively low inertia mounted for free rotation relatively to said shaft, and adapted to control the other of said groups of switches; abutting means on said latter-mentioned disk; and a further member secured against rotation relatively to said shaft, and adapted to cooperate with said latter-mentioned abutting means for driving said latter-mentioned disk.

6. A speed responsive device for adjusting control means of the speed of a rotary system, comprising a rotary drum driven by said rotary system; surfaces in frictional cooperation with said drum; masses associated with said surfaces, subject to centrifugal force, and adapted to urge said surfaces away from said drum; pivotal supports carrying said masses; a shaft substantially secured against rotation relatively to said supports; spring means associated with said supports for urging said surfaces towards said drum; means for adjusting the stress of said spring means; a differential gear train associated on the one hand with said rotary system, and on the other hand with said shaft; a member cooperating with said differential gear train, adapted to move at a velocity corresponding to the differential velocity or said rotary system with respect to said shaft; two mechanical transmissions of different gear ratios between said member and said control means; a clutch in each of said transmissions; and clutch control means responsive to the directional components of the acceleration and velocity of said member for coupling the lower gear ratio transmission when. said directional components of the acceleration and velocity of said member are in the same direction, and for coupling the higher gear ratio transmission when said directional components of the acceleration and velocity of said member are in the opposite direction.

7. A device according to claim 6, further comprising torque responsive means, on the shaft, for urging said surfaces towards said drum when the torque on the shaft increases, and away from said drum when the torque decreases.

8. A device according to claim 6, wherein the spring means and the means for adjusting the stress thereof, comprise a threaded sleeve mounted on said shaft and secured against rotation relatively to said supports; a nut screwed on said ting at one end thereof against said nut; a piston abutment at the other end of said spring, associated with said supports for urging said surfaces towards said drum; connecting means between said nut and said rotary system for rotatingly driving said nut; a clutch in said connecting means; and means for controlling said clutch.

9. In a helicopter having a rotor carrying blades of variable pitch driven by an engine and provided with means for adjusting the pitch of said blades and means for adjusting the power output of said engine, a speed responsive device comprising a reference source of constant-velocity rotation; a differential gear train associated on the one hand with said rotor, and on the other hand with said reference source; a member cooperating with said diiferential gear train, adapted to move at a velocity corresponding to the differential velocity of said rotor with respect to said reference source; an epicycloidal gear train including a sun-gear, a planet-gear meshing with said sun-gear, a shaft fast with said planet-gear, a further planet-gear fast with said shaft, and a further sun-gear meshing with said further planet-gear, and substantially coaxial with said former-mentioned sun-gear; a lever freely supporting said shaft; pivotal supports for said lever substantially coaxial with said sun-gears; displaceable connecting means between said lever and one of said adjusting means; displaceable connecting means between said lattor-mentioned sun-gear and the other of said adjustin means; abutting means for limiting the displacements of said connecting means; means for individually locking said connecting means against displacement; means for selectively controlling said locking means; two mechanical transmissions of diiferent gear ratios between said member and said former-mentioned sungear; a clutch in each of said transmissions; and clutch control means responsive to the directional components of the acceleration and velocity of said member for coupling the lower gear ratio transmission when said directional components of the acceleration and velocity of said member are in the same direction, and for couplin the higher gear ratio transmission when said directional components of the acceleration and velocity of said member are in the opposite direction.

10. A device according to claim 9, wherein the former-mentioned connecting means connects the lever to the pitch adjusting means, whereas the latter-mentioned connecting means connects the latter-mentioned sun-gear to the power output adjusting means, and wherein the locking means corresponding to the power output adjusting means are urged into unlocking position, whereas the locking means corresponding to the pitch adjusting means are urged into locking position, the control means of said locking means being actuated for bringing the former-mentioned locking means into locking position, while simultaneously bringing the latter-mentioned locking means into unlocking position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,269,332 Bench Jan. 6, 1942 2,329,216 Peters Sept. 14-, 1943 2,399,685 McCoy May 7, 1946 2,455,378 McCoy Dec. 7, 1948 

